Novel medical electrical lead for spinal cord stimulation

ABSTRACT

A medical electrical lead for spinal cord stimulation includes first column of electrode surfaces and a second columns of electrode surfaces extending alongside and spaced apart from the first column.

TECHNICAL FIELD

The present invention is related to spinal cord stimulation therapy andmore particularly to medical electrical leads for delivering thestimulation therapy.

BACKGROUND

Electrical stimulation of a spinal cord, which induces pain-relievingparesthesia, can be provided by implantable systems that includeelectrodes coupled to elongate electrical leads. Such electrodes may bepercutaneously or surgically introduced into the epidural spacesurrounding the spinal cord. Medical electrical leads which include anarray of electrodes provide flexibility for selection from a variety ofstimulation patterns upon implantation without having to physicallyreposition the lead within the epidural space. Such leads, wherein theelectrode array is coupled along a body of the lead or along a distalpaddle-like termination of the lead body, are known in the art. However,there is still a need for new spinal cord lead designs including distalends that fit securely within the epidural space surrounding the spinalcord, and conform to the spinal cord so that an array or plurality ofelectrodes coupled to the distal end are in intimate contact with thedura mater enclosing the spinal cord.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of particular embodiments of thepresent invention and therefore do not limit the scope of the invention.The drawings are not to scale (unless so stated) and are intended foruse in conjunction with the explanations in the following detaileddescription. Embodiments of the present invention will hereinafter bedescribed in conjunction with the appended drawings, wherein likenumerals denote like elements.

FIG. 1A is a plan view of a medical electrical lead, according to someembodiments of the present invention.

FIG. 1B is an end view of the lead shown in FIG. 1A.

FIG. 1C is a section view, through section line D-D of FIG. 1A.

FIGS. 2A-B are a perspective views of the lead shown in FIG. 1A.

FIG. 3A is a schematic including a portion of the spinal canal cut awayso that the lead of FIG. 1A may be seen implanted in the epidural spacesurrounding a spinal cord.

FIG. 3B is an end view of the implanted lead shown in FIG. 3A.

FIG. 4 is a plan view including a partial section of a portion of a leadbody assembly, according to some embodiments of the present invention.

FIGS. 5A-B are plan views of mating mold halves, which may be used tocouple lead bodies, according to some methods of the present invention.

DETAILED DESCRIPTION

The following detailed description is exemplary in nature and is notintended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the following description providespractical illustrations for implementing exemplary embodiments of thepresent invention. Examples of constructions, materials, dimensions, andmanufacturing processes are provided for selected elements, and allother elements employ that which is known to those of skill in the fieldof the invention. Those skilled in the art will recognize that many ofthe examples provided have suitable alternatives that can be utilized.

FIG. 1A is a plan view of a medical electrical lead 100, according tosome embodiments of the present invention. FIG. 1A illustrates lead 100including a first column 12 of electrodes AE1-AE8 and a second column 14of electrodes BE1-BE8 coupled to an insulative distal portion 10, whichmay be formed from silicone rubber; a first lead body A and a secondlead body B each extend proximally from distal portion 10 tocorresponding connectors 102 and 104. According to the illustratedembodiment, each lead body A, B includes a plurality of insulatedconductors; each conductor of each of the pluralities of conductorscouples a corresponding electrode of electrodes AE1-AE8 and BE1-BE8 to acorresponding connector contact of contacts AC1-AC8 and BC1-BC8,according to methods known to those skilled in the art, which will bedescribed in greater detail below. Those skilled in the art willappreciate that connectors 102 and 104 may either be connected directlyto a stimulation device or to an extension, or adaptor, which includesone or two connectors for connection with the stimulation device. FIG.1A further illustrates a strain relief 15 extending proximally fromdistal portion 10 over lead bodies A, B.

FIG. 1B is an end view of lead 100; and FIG. 1C is a section viewthrough section line D-D of FIG. 1A. FIGS. 1B-C illustrate each ofelectrodes AE1-AE8 of first column 12 and each of electrodes BE1-BE8 ofsecond column 14 including an approximately planar electrode surface 11;each electrode surface 11 of first column 12 is angled toward eachelectrode surface 11 of second column 14, such that planes (representedby dashed lines in FIG. 1C), which extend along and approximatelyorthogonally out from each column 12, 14 intersect one another.According to an exemplary embodiment of the present invention, a surfacearea of each electrode surface 11 is approximately six squaremillimeters, a longitudinal spacing between each electrode AE1-AE8 andBE1-BE8, within each column 12, 14 is approximately four millimeters,edge-to-edge, and approximately seven millimeters, center-to-center, anda spacing between columns 12 and 14 is between approximately three andfour millimeters, center-to-center, and between approximately one andtwo millimeters, edge-to-edge. Although FIG. 1A illustrates eachelectrode surface 11 of first column 12 longitudinally aligned with thecorresponding electrode surface 11 of second column 14, the scope of thepresent invention is not so limited, and alternate embodiments mayinclude staggered columns of electrode surfaces. Furthermore, alternateembodiments of the present invention can include electrode surfaceshaving a convex curvature rather than being approximately planar, asillustrated.

FIGS. 1B-C further illustrate distal portion 10 including a firstsurface 13 extending between an inner edge 602 of each electrode surface11 of first column 12 and an inner edge 604 of each electrode surface 11of second column 14, and a second surface 16 extending from an outeredge 612 of each electrode surface 11 of first column 12 to an outeredge 614 of each electrode surface 11 of second column 14. According tothe illustrated embodiment, first surface 13 curves in a concave fashionand second surface 16 extends behind first and second columns 12, 14 andincludes an approximately flat portion 17 disposed opposite first andsecond columns 12, 14. FIGS. 2A-B are perspective views of lead 100,which further illustrate first surface 13 and flat portion 17 of secondsurface 16. According to an exemplary embodiment, distal portion has alength between approximately sixty millimeters and approximately seventymillimeters, a width between approximately eight and approximatelytwelve millimeters, and a thickness, defined from flat portion 17 ofsurface 16 across to first surface 13, of approximately two millimeters;and, surface 13 has a radius of curvature of approximately ninemillimeters.

FIG. 1C further illustrates electrodes AE6 and BE6, representative ofeach electrode of columns 12 and 14, respectively, extending, in acantilever fashion, laterally away from respective lead bodies A, B,which extend into distal portion 10. Each electrode AE1-AE8 and BE1-BE6may be coupled, as such, for example, by laser welding, directly to therespective conductor within the corresponding lead body A, B, or to aconductive ring, which is coupled to the respective conductor anddisposed about the corresponding lead body A, B. According to theillustrated embodiment, surface 11 of each electrode AE1-AE8 and BE1-BE6protrudes slightly from adjacent portions of surfaces 13, 16, but,according to alternate embodiments, electrode surfaces 11 are flush withadjacent portions of surfaces 13, 16.

FIG. 3A is a schematic including a portion of the spinal canal cut awayso that lead 100 may be seen implanted in the epidural space of a spinalcord 30; and FIG. 3B is an end view of the implanted lead 100. FIGS.3A-B illustrate distal portion 10 of lead implanted in the epiduralspace such that electrode surfaces 11 are in intimate contact with thedura mater 35 surrounding spinal cord 30. Methods for implantingsurgical spinal cord leads, such as lead 100, are well known to thoseskilled in the art. With reference to FIGS. 3A-B, it may be appreciatedthat the pre-formed profile of distal portion 10, along with the angledarrangement of electrode surfaces 11, as described in conjunction withFIG. 1C, may greatly enhance the conformance of distal portion 10 aboutspinal cord 30 such that electrodes 11 contact the dura mater 35, asshown, for relatively efficient stimulation of spinal cord 30.Furthermore, the preformed shape of distal portion 10 facilitates thefit of distal portion 10 within the epidural space.

FIG. 4 is a plan view including a partial section of a portion of a leadbody assembly 40, according to some embodiments of the presentinvention. FIG. 4 illustrates assembly 40 including four conductors451-454 wound in a coil 45 and each conductor 451-454 coupled to aconductive ring 401-404, respectively, which is, in turn, coupled to anelectrode 41-44, respectively. Conductors 451-454 are isolated from oneanother by an overlay of insulation material surrounding each ofconductors 451-454, examples of which include, but are not limited to,polyimide, polytetrafluoroethylene (PTFE), and ethylenetetrafluoroethylene (ETFE). According to the illustrated embodiment, adistal end of each conductor 451-454 is hooked in a slot of thecorresponding conductive ring 401-404, and laser welded thereto, andeach electrode 41-44, whose active electrode surface is shown facinginto the page, is coupled to the corresponding ring 401-404 via a laserweld, for example, as illustrated along line 440. Those skilled in theart will appreciate that conductor 45 extends proximally to a connector,for example, similar to connectors 102 and 104 of FIG. 1A, where eachconductor 451-454 is coupled to a corresponding connector contact, forexample, in manner similar to that described for rings 401-404. AlthoughFIG. 4 illustrates assembly 40 including only four conductors andelectrodes, it should be understood that lead body A or lead body B, ofFIG. 1A, which each include eight conductors and electrodes, mayincorporate an assembly constructed in a similar manner to that ofassembly 40, but including four additional conductors, rings andelectrodes.

According to certain methods of the present invention, a step ofcoupling electrodes to rings, for example, as illustrated in FIG. 4, isperformed prior to coupling two of lead body assemblies 40 together.According to some embodiments of the present invention, conductive rings401-404 may form electrode surfaces of completed lead assemblies thatinclude assembly 40, and have been originally manufactured forindependent use, for example, as percutaneous spinal cord stimulationleads. However, alternate embodiments of the present invention need notinclude conductive rings, such as rings 401-404, and each electrode, forexample, electrodes 41-44, may be coupled directly to a correspondingconductor, for example, conductors 452-453.

FIG. 4 further illustrates insulation members 46, 47, 48 and 49 eachextending around a portion of coil 45. According to some methods of thepresent invention, after electrodes 41-44 are coupled to rings 401-404,an adhesive, for example, silicone medical adhesive, is injected, perarrow C, to fill lumens of members 46, 47, 48 and 49, prior to couplinga two of assemblies 40 together.

Coupling two of assemblies 40 together may be accomplished by forming apaddle-like insulative member around the pair assemblies 40 either by atransfer or an insert molding method, known to those skilled in the art;the paddle-like member, according to some embodiments is similar todistal portion 10 described in conjunction with FIGS. 1A-2B. FIGS. 5A-Bare plan views of mating mold halves 51, 53, which may be used to couplelead bodies, via a transfer molding method, after electrodes 41-44 havebeen coupled to conductors 451-454. FIG. 5A illustrates first mold half51 including a cavity 512 for forming, in conjunction with a cavity 532of mating mold half 53 shown in FIG. 5B, a paddle-like insulative distalportion, for example, distal portion 10 illustrated in FIGS. 1A-2B.

FIG. 5A further illustrates electrode reliefs 514 disposed at locationsin cavity 512 to correspond with positions of electrode surfaces ofelectrodes 41-44 of each of two assemblies 40 that will be placedbetween mold halves 51, 53. Reliefs 514 prevent the flow of injectedmaterial, for example, MDX silicone rubber, which forms the paddle-likemember, into sites corresponding to electrode surfaces of electrodes41-44, so that the electrode surfaces will not be covered with theinsulative material.

FIG. 5B further illustrates mold half 53 including a relief 518 forplacement of a sheet of mesh material, which will be embedded within thepaddle-like member, for example, as illustrated in FIG. 1C where themesh is denoted by item number 18. Mesh 18 may enhance the structuralintegrity of the coupling of lead bodies A and B by distal portion 10.After the molding process is completed, excess mesh material may betrimmed away about the perimeter of the paddle-like member.

Referring back to FIGS. 1A-2B, it may be appreciated that a profile ofcavity 512, in between reliefs 514, may have a convex curvature, forexample, to form surface 13, and a profile of cavity 513 may include aflat portion, for example, to form surface 17. It should be noted that,although a transfer molding process calls for the injection of thematerial into mating cavities 512, 513 prior to insertion of assemblies40 between mold halves 51, 53, other types of molding processes, whichare within the scope of the present invention, for example, insertmolding, call for insertion of assemblies 40 into a mold, prior to theinjection of the material.

In the foregoing detailed description, the invention has been describedwith reference to specific embodiments. However, it may be appreciatedthat various modifications and changes can be made without departingfrom the scope of the invention as set forth in the appended claims.

1. A medical electrical lead for spinal cord stimulation, comprising: afirst column of approximately planar electrode surfaces; and a secondcolumn of approximately planar electrode surfaces extending alongside,and spaced apart from the first column; each electrode surface of thefirst column angled toward each electrode surface of the second columnsuch that a plane extending along the first column and orthogonally outfrom the electrode surfaces of the first column intersects a planeextending along the second column and orthogonally out from theelectrode surfaces of the second column.
 2. The lead of claim 1, furthercomprising a distal portion to which the first and second columns ofelectrode surfaces are coupled and wherein the distal portion includes asurface extending along and between the first and second columns ofelectrode surfaces.
 3. The lead of claim 2, wherein the distal portionsurface extends from an inner edge of each electrode surface of thefirst column to an inner edge of each electrode surface of the secondcolumn.
 4. The lead of claim 3, wherein the distal portion surface iscurved.
 5. The lead of claim 2, wherein the distal portion surfaceextends from an outer edge of each electrode surface of the first columnto an outer edge of each electrode surface of the second column.
 6. Thelead of claim 5, wherein the distal portion surface includes a flatportion disposed opposite the first and second columns of electrodesurfaces.
 7. The lead of claim 1, wherein each electrode surface of thefirst column is longitudinally aligned with a corresponding electrodesurface of the second column.
 8. The lead of claim 2, furthercomprising: a first lead body extending within the distal portion, thefirst lead body including a first plurality of conductors isolated fromone another, and each of the first plurality of conductors coupled to acorresponding electrode surface of the first column of electrodesurfaces; and a second lead body extending within the distal portion,the second lead body including a second plurality of conductors isolatedfrom one another, and each of the second plurality of conductors coupledto a corresponding electrode surface of the second column of electrodesurfaces.
 9. The lead of claim 8, further comprising a mesh panelextending between the first and second lead bodies within the distalportion.
 10. The lead of claim 2, further comprising: a first connectorextending proximally from the distal portion and including a firstplurality of contact surfaces, each contact surface coupled to acorresponding electrode surface of the first column of electrodesurfaces; and a second connector extending proximally from the distalportion and including a second plurality of contact surfaces, eachcontact surface coupled to a corresponding electrode surface of thesecond column of electrode surfaces.
 11. A medical electrical lead forspinal cord stimulation, comprising: a first elongate lead bodyincluding a first plurality of conductors isolated from one another; asecond elongate lead body including a second plurality of conductorsisolated from one another; a distal portion coupling the first lead bodyto the second lead body, the first and second lead bodies extendingproximally from the distal portion; a first column of electrode surfacescoupled to the distal portion, each of the electrode surfaces of thefirst column coupled to a corresponding conductor of the first pluralityof conductors and extending laterally away from the first lead body; anda second column of electrode surfaces coupled to the distal portion andextending alongside, and spaced apart from the first column, each of theelectrode surfaces of the second column coupled to a correspondingconductor of the second plurality of conductors and extending laterallyaway from the second lead body.
 12. The lead of claim 11, wherein thedistal portion includes a surface extending from an inner edge of eachelectrode surface of the first column to an inner edge of each electrodesurface of the second column.
 13. The lead of claim 12, wherein thedistal portion surface is curved.
 14. The lead of claim 11, wherein thedistal portion includes a surface extending from an outer edge of eachelectrode surface of the first column to an outer edge of each electrodesurface of the second column.
 15. The lead of claim 14, wherein thedistal portion surface includes a flat portion disposed opposite thefirst and second columns of electrode surfaces.
 16. The lead of claim11, wherein each electrode surface of the first column is longitudinallyaligned with a corresponding electrode surface of the second column. 17.The lead of claim 11, further comprising a mesh panel extending betweenthe first and second lead bodies within the distal portion.
 18. The leadof claim 11, wherein each of the electrode surfaces of the first andsecond columns are approximately planar.
 19. The lead of claim 18,wherein each electrode surface of the first column is angled toward eachelectrode surface of the second column such that a plane extending alongthe first column and orthogonally out from the electrode surfaces of thefirst column intersects a plane extending along the second column andorthogonally out from the electrode surfaces of the second column.
 20. Amedical electrical lead for spinal cord stimulation, comprising: a firstelongate lead body including a distal portion, the distal portion of thefirst lead body including a first column of electrode surfaces coupledthereto; a second elongate lead body including a distal portion, thedistal portion of the second lead body including a second column ofelectrode surfaces coupled thereto; and a paddle-like member couplingthe first lead body distal portion to the second lead body distalportion, the paddle-like member being formed by injection molding overthe distal portions and including a first side, along which theelectrode surfaces of the first and second columns are exposed, and asecond side enclosing the distal portions.
 21. The lead of claim 20,wherein the electrode surfaces of the first and second columns areapproximately planar.
 22. The lead of claim 21, wherein each electrodesurface of the first column is angled toward each electrode surface ofthe second column such that a plane extending along the first column andorthogonally out from the electrode surfaces of the first columnintersects a plane extending along the second column and orthogonallyout from the electrode surfaces of the second column.
 23. The lead ofclaim 20, wherein each electrode surface of the first column islongitudinally aligned with a corresponding electrode surface of thesecond column.
 24. The lead of claim 20, wherein the first side of thedistal portion includes a concave surface extending between theelectrode surfaces of the first and second columns.
 25. The lead ofclaim 20, further comprising a mesh panel extending between the distalportions of the first and second lead bodies.
 26. The lead of claim 20,further comprising: a first connector extending proximally from thefirst lead body and including a first plurality of contact surfaces,each contact surface coupled to a corresponding electrode surface of thefirst column of electrode surfaces; and a second connector extendingproximally from the second lead body and including a second plurality ofcontact surfaces, each contact surface coupled to a correspondingelectrode surface of the second column of electrode surfaces.
 27. Thelead of claim 20, wherein: the distal portion of the first lead bodyfurther includes a first plurality of conductive rings longitudinallyspaced apart from one another and separated from one another by a firstset of insulating members; the distal portion of the second lead bodyfurther includes a second plurality of conductive rings longitudinallyspaced apart from one another and separated by one another by a secondset of insulating members; each electrode surface of the first column iswelded to a corresponding conductive ring of the first plurality ofconductive rings; and each electrode surface of the second column iswelded to a corresponding conductive ring of the second plurality ofconductive rings.
 28. The lead of claim 20, wherein each of the firstand second lead bodies is formed by a medical electrical lead of a typehaving a generally cylindrical configuration adapted for percutaneousimplantation.
 29. The lead of claim 20, wherein the second side of thepaddle-like member includes an approximately flat surface extendingbetween the first and second columns.
 30. A medical electrical lead forspinal cord stimulation, comprising: a distal portion including a firstside and a second side opposite the first side; a first column ofelectrode surfaces mounted in the distal portion and exposed along thefirst side; and a second column of electrode surfaces mounted in thedistal portion and exposed along the first side, the second column beingspaced apart from the first column and extending alongside the firstcolumn; wherein the first side of the distal portion includes a concaveportion extending between the electrode surfaces of the first and secondcolumns and the second side of the distal portion includes a flatportion extending between the first and second columns.
 31. The lead ofclaim 30, wherein each electrode surface of the first and second columnsis approximately planar.
 32. The lead of claim 31, wherein eachelectrode surface of the first column is angled toward each electrodesurface of the second column such that a plane extending along the firstcolumn and orthogonally out from the electrode surfaces of the firstcolumn intersects a plane extending along the second column andorthogonally out from the electrode surfaces of the second column. 33.The lead of claim 30, wherein each electrode surface of the first columnis longitudinally aligned with a corresponding electrode surface of thesecond column.
 34. The lead of claim 30, further comprising: a firstlead body extending within the distal portion, the first lead bodyincluding a first plurality of conductors isolated from one another, andeach of the first plurality of conductors coupled to a correspondingelectrode surface of the first column of electrode surfaces; and asecond lead body extending within the distal portion, the second leadbody including a second plurality of conductors isolated from oneanother, and each of the second plurality of conductors coupled to acorresponding electrode surface of the second column of electrodesurfaces.
 35. The lead of claim 34, wherein each electrode surface ofthe first column extends laterally away from the first lead body andeach electrode surface of the second column extends laterally away fromthe second lead body.